Moving-picture temporal scalable coding method, coding apparatus, decoding method, decoding apparatus, and computer program therefor

ABSTRACT

In temporal scalable moving-picture video signal coding, an input interlaced moving-picture video signal is converted into a progressive moving-picture video signal at the same frame rate as the interlaced moving-picture video signal. The progressive moving-picture video signal is coded to produce a first bitstream. Fields of the interlaced moving-picture video signal are coded with inter-picture prediction using a locally decoded picture signal as a reference video signal, thus producing a second bitstream. The fields are different in time from frames of the progressive moving-picture video signal. The locally decoded picture signal are produced by locally decoding the progressive moving-picture video signal. The first and second bitstreams are multiplexed into an output temporal scalable moving-picture video bitstream.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a moving-picture temporalscalable coding method and a moving-picture temporal scalable codingapparatus, a moving-picture temporal scalable decoding method and amoving-picture temporal scalable decoding apparatus, and also a computerprogram for performing the coding or the decoding method.

[0002] Moving-picture coding is classified into simple one-layer codingand scalable coding for encoding two-layer bitstreams. The latter allowsdecoding a bitstream of a base layer only and also decoding a bitstreamof an enhancement layer, decoded base-layer and enhancement-layerpictures being combined to reproduce high-quality pictures.

[0003] Scalable coding is classified into SNR (Signal-to-Noise Ratio),spatial, and temporal scalable coding. The temporal scalable coding isto decimate, for example, a 60-fps (field per second) interlaced imageper field to obtain a 30-fps image and encode this 30-fps image whilepredicting the remaining non-encoded fields by using a locally decodedimage of the encoded fields and encode prediction residuals.

[0004] In known moving-picture temporal scalable coding, a 60-fpsinterlaced moving-picture video signal is divided into even-numberfields and odd-number fields.

[0005] The even-number fields are subjected to coding while theodd-number fields are subjected to delay.

[0006] In coding, a video signal carrying 30-fps even-number fields iscoded into a bitstream and quantization resultants (not a bitstream butsignal components at least quantized). The coding technique may be MPEGinter-picture predictive coding or intrafield coding.

[0007] The quantization resultants are subjected to local decoding to bereproduced into a local decoded picture. The local picture is subjectedto inter-picture prediction to produce a predictive signal for eachodd-number field.

[0008] In delaying, each odd-number field is delayed until thepredictive signal is produced based on each even-number field, asexplained above.

[0009] The predictive signal is subtracted from an odd-number-fielddelayed signal to obtain a prediction residual.

[0010] The prediction residual is subjected to DCT (Discrete CosineTransform). The resultant 8×8 DCT coefficients are subjected toquantization at a given step width. The resultant fixed-lengthcoefficients (prediction residual) are subjected to variable-lengthcoding to obtain a bitstream.

[0011] This bitstream is multiplexed with the bitstream already obtainedfrom the even-number fields, as an output moving-picture bitstream undertemporal scalable coding.

[0012] In summary, under the known temporal scalable coding, aninterlaced moving-picture video signal is divided into even-numberfields and odd-number fields. The even-number fields are converted intoa base-layer bitstream while the odd-number fields an enhancement-layerbitstream, or vice versa.

[0013] The base-layer bitstream and the enhancement-layer bitstream aremultiplexed with each other to form an output moving-picture bitstreamunder temporal scalable coding, as illustrated in FIG. 1.

[0014] In FIG. 1, a sign “field” indicates one field of an interlacedvideo. The numbers attached to the signs “field” indicate the order ofcoded pictures. Base-layer pictures come before enhancement-layerpictures for bi-directional prediction of the enhancement-layerpictures, even though the former pictures come after the latter picturesin the time domain. The reverse order is further required among thebase-layer pictures when bi-directional prediction is performed forthese pictures.

[0015] In known moving-picture temporal scalable decoding, amoving-picture bitstream obtained from a 60-fps interlacedmoving-picture video signal by temporal scalable coding, is divided intoa base-layer bitstream, an enhancement-layer bitstream, and a scalefactor.

[0016] The base-layer bitstream is decoded so that a 30-fps video signalis reproduced. The reproduced signal carries even-number fields of the60-fps interlaced moving-picture video signal. The reproduced signal issubjected to inter-picture prediction to produce a prediction signal forodd-number fields of the interlaced moving-picture video signal.

[0017] The enhancement-layer bitstream is subjected to variable-lengthdecoding so that variable-length codes of prediction residual isreconverted into fixed-length codes.

[0018] The fixed-length codes are subjected to dequantization at a givenquantization parameter to be reproduced into DCT coefficients ofprediction residual.

[0019] The DCT coefficients are subjected to inverse DCT so that 8×8 DCTcoefficients are converted into a decoded prediction-residual signal.

[0020] The decoded prediction-residual signal is added to the predictionsignal already produced to form a 30-fps decoded video signal. Thisdecoded signal carries the odd-number fields of the 60-fps interlacedmoving-picture video signal.

[0021] The odd-number fields of the 30-fps decoded video signal and theeven-number fields of the 30-fps video signal are selected insynchronism with the scale factor. The latter video signal carrying theeven-number fields have already been decoded and delayed until theformer video signal is decoded.

[0022] The odd-/even number field selection reproduces the 60-fpsinterlaced moving-picture video signal.

[0023] As explained, under the known temporal scalable coding, aninterlaced moving-picture video signal is divided into even-numberfields and odd-number fields. The even-number fields are converted intobase-layer bitstream while the odd-number fields an enhancement-layerbitstream, or vise versa.

[0024] The known temporal scalable coding, however, has severaldrawbacks.

[0025] Base-layer coding causes many prediction errors inmotion-compensated inter-picture prediction due to many aliasingcomponents involved in field pictures.

[0026] Enhancement-layer coding suffers inaccurate inter-pictureprediction due to difference in parity (even/odd) of fields betweenpictures to be coded and prediction reference pictures.

[0027] These two factors drastically lower coding efficiency in theknown temporal scalable coding compared to other coding techniques.

SUMMARY OF THE INVENTION

[0028] A purpose of the present invention is to provide a moving-picturetemporal scalable coding method and a moving-picture temporal scalablecoding apparatus that achieve high coding efficiency in coding ofinterlaced moving-picture video signals, a moving-picture temporalscalable decoding method and a moving-picture temporal scalable decodingapparatus for decoding the video signals coded by the coding method andapparatus, respectively, and also a computer program for performing thecoding or the decoding method.

[0029] The present invention provides a temporal scalable moving-picturevideo signal coding method comprising the steps of: converting an inputinterlaced moving-picture video signal into a progressive moving-picturevideo signal at the same frame rate as the -interlaced moving-picturevideo signal; encoding the progressive moving-picture video signal toproduce a first bitstream; encoding fields of the interlacedmoving-picture video signal, the fields being different in time fromframes of the progressive moving-picture video signal, withinter-picture prediction using a locally decoded picture signal as areference video signal, the locally decoded picture signal beingproduced by locally decoding the progressive moving-picture videosignal, thus producing a second bitstream; and multiplexing the firstand second bitstreams into an output temporal scalable moving-picturevideo bitstream.

[0030] Moreover, the present invention provides a temporal scalablemoving-picture video signal decoding method comprising the steps of:demultiplexing a bitstream produced by temporal scalable moving-picturecoding into a first bitstream and a second bitstream, the firstbitstream having been produced by encoding a progressive moving-picturevideo signal at the same frame rate as an interlaced moving-picturevideo signal to be reproduced, the second bitstream having been producedby encoding fields of the interlaced moving-picture video signal, thefields being different in time from frames of the progressivemoving-picture video signal; decoding the first bitstream to reproduce aprogressive moving-picture video signal; converting the reproducedprogressive moving-picture video signal into a first field video signalhaving either even- or odd-number fields of the interlacedmoving-picture video signal; decoding the second bitstream withinter-picture prediction using the reproduced progressive moving-picturevideo signal as a reference video signal, thus producing a second fieldvideo signal having fields of the interlaced moving-picture videosignal, the fields of the second field video signal being different inparity from the fields of the first field video signal; and switchingthe first field video signal and the second field video signal to outputthe interlaced moving-picture video signal.

[0031] Furthermore, the present invention provides a temporal scalablemoving-picture video signal coding apparatus comprising: a converter toconvert an input interlaced moving-picture video signal into a.progressive moving-picture video signal at the same frame rate as theinterlaced moving-picture video signal; a first bitstream generator toencode the progressive moving-picture video signal, thus generating afirst bitstream; a second bitstream generator to encode fields of theinterlaced moving-picture video signal, the fields being different intime from frames of- the progressive moving-picture video signal, withinter-picture prediction using a locally decoded picture signal as areference video signal, the locally decoded picture signal beingproduced by locally decoding the progressive moving-picture videosignal, thus producing a second bitstream; and a multiplexer tomultiplex the first and second bitstreams into an output temporalscalable moving-picture video bitstream.

[0032] Moreover, the present invention provides a temporal scalablemoving-picture video signal decoding apparatus comprising: ademultiplexer to demultiplex a bitstream produced by temporal scalablemoving-picture coding into a first bitstream and a second bitstream, thefirst bitstream having been produced by encoding a progressivemoving-picture video signal at the same frame rate as an interlacedmoving-picture video signal to be reproduced, the second bitstreamhaving been produced by encoding fields of the interlaced moving-picturevideo signal, the fields being different in time from frames of theprogressive moving-picture video signal; a first decoder to decode thefirst bitstream to reproduce a progressive moving-picture video signal;a converter to convert the reproduced progressive moving-picture videosignal into a first field video signal having either even- or odd-numberfields of the interlaced moving-picture video signal; a second decoderto decode the second bitstream with inter-picture prediction using thereproduced progressive moving-picture video signal as a reference videosignal, thus producing a second field video signal having fields of theinterlaced moving-picture video signal, the fields of the second fieldvideo signal being different in parity from the fields of the firstfield video signal; and a switch to switch the first field video signaland the second field video signal to output the interlacedmoving-picture video signal.

[0033] Furthermore, the present invention provides acomputer-implemented method for temporal scalable moving-picture videosignal coding comprising the steps of: converting an input interlacedmoving-picture video signal into a progressive moving-picture videosignal at the same frame rate as the interlaced moving-picture videosignal; encoding the progressive moving-picture video signal to producea first bitstream; encoding fields of the interlaced moving-picturevideo signal, the fields being different in time from frames of theprogressive moving-picture video signal, with inter-picture predictionusing a locally decoded picture signal as a reference video signal, thelocally decoded picture signal being produced by locally decoding theprogressive moving-picture video signal, thus producing a secondbitstream; and multiplexing the first and second bitstreams into anoutput temporal scalable moving-picture video bitstream.

[0034] Still furthermore, the present invention provides acomputer-implemented method for temporal scalable moving-picture videosignal decoding comprising the steps of: demultiplexing a bitstreamproduced by temporal scalable moving-picture coding into a firstbitstream and a second bitstream, the first bitstream having beenproduced by encoding a progressive moving-picture video signal at thesame frame rate as an interlaced moving-picture video signal to bereproduced, the second bitstream having been produced by encoding-fields of the interlaced moving-picture video signal, the fields beingdifferent in time from frames of the progressive moving-picture videosignal; decoding the first bitstream to reproduce a progressivemoving-picture video signal; converting the reproduced progressivemoving-picture video signal into a first field video signal havingeither even- or odd-number fields of the interlaced moving-picture videosignal; decoding the second bitstream with inter-picture predictionusing the reproduced progressive moving-picture video signal as areference video signal, thus producing a second field video signalhaving fields of the interlaced moving-picture video signal, the fieldsof the second field video signal being different in parity from thefields of the first field video signal; and switching the first fieldvideo signal and the second, field video signal to output the interlacedmoving-picture video signal.

BRIEF DESCRIPTION OF DRAWINGS

[0035]FIG. 1 is an illustration of a moving-picture bitstream underknown temporal scalable coding;

[0036]FIG. 2 is a block diagram of a first embodiment of amoving-picture temporal scalable coding apparatus according to thepresent invention;

[0037]FIG. 3 is an illustration of the structure of scanning lines in aninput interlaced moving-picture signal, a base-layer moving-picturesignal, and an enhancement-layer moving-picture signal, in the firstembodiment of the moving-picture temporal scalable coding apparatusaccording to the present invention;

[0038]FIG. 4 is a block diagram of a second embodiment of amoving-picture temporal scalable coding apparatus according to thepresent invention;

[0039]FIG. 5 is a block diagram of a first embodiment of amoving-picture temporal scalable decoding apparatus according to thepresent invention;

[0040]FIG. 6 is a block diagram of a second embodiment of amoving-picture temporal scalable decoding apparatus according to thepresent invention;

[0041]FIG. 7 is an illustration of the structure of a moving-picturetemporal scalable bitstream produced by the first embodiment of themoving-picture temporal scalable coding apparatus according to thepresent invention;

[0042]FIG. 8 is an illustration of the structure of a moving-picturetemporal scalable bitstream produced by the second embodiment of themoving-picture temporal scalable coding apparatus according to thepresent invention;

[0043]FIG. 9 is a flowchart indicating a sequence of a computer programfor moving-picture temporal scalable coding according to the presentinvention;

[0044]FIG. 10 is a flowchart indicating a sequence of a computer programfor moving-picture temporal scalable decoding according to the presentinvention;

[0045]FIG. 11 is a block diagram of an embodiment of a transmitter fortransmitting a temporal scalable coded moving-picture video signalaccording to the present invention;

[0046]FIG. 12 is a flowchart indicating an operation of a transmitterinterface installed in the transmitter shown in FIG. 11;

[0047]FIG. 13 is a block diagram of an embodiment of a receiver forreceiving a temporal scalable coded moving-picture video signalaccording to the present invention; and

[0048]FIG. 14 is a flowchart indicating an operation of a receiverinterface installed in the receiver shown in FIG. 13.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0049] Several embodiments according to the present invention will bedisclosed with reference to the attached drawings.

[0050] Shown in FIG. 2 is a first embodiment of a moving-picturetemporal scalable coding apparatus according to the present invention.

[0051] An input 60-fps (field per second) interlaced moving-picturevideo signal is supplied, via an input terminal 1, to aprogressive-scanning converter 2, a picture selector 7, and a switch 10.

[0052] The progressive-scanning converter 2 interpolates scanning linesfrom scanning lines temporal-spatially adjacent to the former scanninglines, as preprocessing in base-layer coding. The former scanning lineshave been decimated from the input interlaced video signal. Theinterpolation produces a progressive video signal having 60 frames persecond with scanning lines two times those of the input interlaced videosignal.

[0053] The progressive video signal is supplied to a switch 3 via whichevery second frame is decimated to produce a 30-FPS progressive videosignal having 30 frames per second. In the following disclosure, theabbreviation “fps” means “field per second” whereas “FPS” means “frameper second”.

[0054] The progressive-scanning converter 2 and the switch 3 may work atthe same time to obtain the 30-FPS progressive video signal directlyfrom the input interlaced video signal. One requirement is thatscanning-line interpolation is performed while the scanning lines of theinput video signal remain, to form each progressive frame that exists inthe same timing as a field of the input video signal, not an incompleteeven- or odd-number filed picture.

[0055] The 30-FPS progressive video signal is then supplied to encoder4. The encoder 4 encodes the video signal and produces a base-layerbitstream (a first bitstream). The base-layer bitstream is supplied to amultiplexer 5 while quantization resultants are supplied to a localdecoder 9. The coding technique used in the encoder 4 may beinter-picture predictive coding, intra frame coding under MPEG-2,MPEG-4, etc.

[0056] The local decoder 9 performs a coding processing to all frames ofthe 30-FPS progressive video signal to obtain a 30-FPS- progressivelocally reproduced picture to be used as a prediction reference picture.All frames are subjected to local decoding in this embodiment whereasbi-directional predictive frames may not always be subjected to localdecoding in MPEG coding.

[0057] The 30-FPS progressive locally reproduced picture is supplied toan inter-picture predictor 8 as a prediction reference picture. Thepredictor 8 produces a progressive prediction signal for each interlacedfield interposed between two frames of the 30-FPS progressive videosignal.

[0058] The progressive prediction signal is supplied to a fielddecimator 11. The decimator 11 converts the progressive predictionsignal into an interlaced prediction signal having fields by decimatingscanning lines of the prediction signal. The inter-picture predictor 8and the field decimator 11 may be combined to obtain the interlacedprediction signal directly from the 30-FPS progressive locallyreproduced prediction reference picture.

[0059] The switch 10 selects fields from the input 60-fps interlacedmoving-picture video signal, different in time from frames selected- bythe switch 3, as preprocessing in enhancement-layer coding. Each fieldto be coded selected by, the switch 10 is supplied to a picture delayer12. The field to be coded is delayed until a reference picture isproduced through the processing from the progressive-scanning converter2 to the local decoder 9 for inter-picture prediction.

[0060] A field video signal is supplied from the picture delayer 12 to asubtracter 13. It is subtracted from the predictive signal supplied fromthe field decimator 11. The resultant residual is supplied to a DCT 14for DCT (Discrete Cosine Transform) processing. The resultant DCTcoefficients are supplied to a quantizer 15 for quantization at a givenstep width. The resultant fixed-length coefficients (predictionresidual) are supplied to a variable-length encoder 16 forvariable-length coding to produce an enhancement-layer bitstream (asecond bitstream).

[0061] The enhancement-layer bitstream is supplied to the multiplexer 5.Index codes are inserted into the enhancement-layer bitstream and thebase-layer bitstream also supplied to the multiplexer 5. Theindex-code-inserted base-layer and enhancement-layer bitstreams aremultiplexed with each other. The multiplexed bitstream is output via acode output terminal 6.

[0062] As disclosed above, in this embodiment, an input interlacedmoving-picture video signal is converted into a progressive video signalat the same frame rate before coding. In other words, this embodimentperforms coding of a progressive moving-picture video signal with noincrease in the number of scanning lines. Therefore, this embodimentoffers a drastically low bit rate compared to coding of an interlacedmoving-picture video signal with no conversion to a progressive videosignal.

[0063] Described next with reference to FIG. 3 is the structure ofscanning lines in the input interlaced moving-picture signal, thebase-layer moving-picture signal, and the enhancement-layermoving-picture signal, in the first embodiment.

[0064] Illustrated in (a) of FIG. 3 is the input 60-fps interlacedmoving-picture video signal. Scanning lines are displaced in a verticaldirection (SVD) from each other between the -even-number and odd-numberfields in the time domain (TIME).

[0065] The 30-FPS progressive video signal, illustrated in (b) of FIG.3, to be coded in the base layer has scanning lines at the same timingas the even-number or the odd-number fields of the input 60-fpsinterlaced moving-picture video signal. This scanning-line structure issuitable for motion compensation with almost no aliasing, thus producingvery few prediction errors.

[0066] Illustrated in (c) of FIG. 3 is the progressive video signal inthe enhancement layer, having scanning lines of either the even-numberor the odd-number fields of the input 60-fps interlaced moving-picturevideo signal, different in parity from the fields shown in (b) of FIG.3. The number of scanning lines to be coded in (c) of FIG. 3 is half ofthose in (a) and (b) of FIG. 3. The progressive video signal indicatedby solid circles is subjected to inter-picture prediction using theother progressive video signal indicated by dot circles on both sides ofeach solid circle with the interval of 1/60 seconds. This inter-pictureprediction produces very few prediction errors and a small of amount ofcodes.

[0067] As disclosed in detail, the first embodiment achieves temporalscalable coding superior to the known temporal scalable coding techniqueand also at higher coding efficiency than the usual interlacedmoving-picture coding technique, to an input interlaced moving-picturevideo signal.

[0068] Shown in FIG. 4 is a second embodiment of a moving-picturetemporal scalable coding apparatus according to the present invention.

[0069] In FIG. 4, the elements the same as or analogous to those shownin FIG. 2 are given the same reference numbers and not disclosed indetail.

[0070] The temporal scalable coding apparatus shown in FIG. 4 have ascanning-line down-sampler 35 and a scanning-line up-sampler 36 comparedto the counterpart in FIG. 2. An encoder 36 and a local decoder 37 shownin FIG. 4 thus operate in different ways from the counterparts 4 and 9in FIG. 2.

[0071] An input 60-fps interlaced moving-picture video signal issupplied, via an input terminal 1, to a progressive-scanning converter2, a picture selector 7, and a switch 10.

[0072] The input 60-fps interlaced moving-picture video signal suppliedto the progressive-scanning converter 2 and then to a switch 3 isconverted into a 30-FPS progressive video signal, like the firstembodiment shown in FIG. 2.

[0073] The 30-FPS progressive video signal is supplied to thescanning-line down-sampler 35. It is down-sampled in a spatial verticaldirection to about ¾ to ⅔ for its scanning lines while subjected to bandlimitation by a vertical low-pass filter of the down-sampler 35.Vertical low-pass filtering is performed to produce no aliasing afterdown-sampling. The number of scanning lines is reduced to 360 or 320when the number of effective scanning lines per frame is 480 for theinput 60-fps interlaced moving-picture video signal. Or, the former isreduced to 810 or 720 when the latter is 1080. The input interlacedvideo signal has been suppressed for its highest frame verticalfrequency components for reducing flickers. Therefore, the video signalconverted into a progressive signal by the progressive-scanningconverter 2 has few highest frame vertical frequency components, thus avery little video information being lost by down-sampling.

[0074] The 30-FPS video signal down-sampled in the spatial verticaldirection is then coded by the encoder 36. The signal supplied to theencoder 36 has the fewer number of scanning lines than that to thecounterpart 4 (FIG. 2). Thus, the amount of processing performed andalso the amount of codes of a base-layer bitstream (a third bitstream)generated by the encoder 36 are smaller than those by the counterpart 4by which all pictures are coded after converted into progressivepictures.

[0075] The 30-FPS video signal coded by the encoder 36 is supplied tothe local decoder 37 for local decoding of all frames of the videosignal. The signal supplied to the local decoder 37 has the fewer numberof scanning lines than that to the counterpart 9 (FIG. 2). Thus, theamount of processing performed by the local decoder 37 is also smallerthan the counterpart 9.

[0076] A locally decoded signal output from the local decoder 37 issupplied to the scanning up-sampler 38 for increase in the scanning lineto the original number before down-sampling.

[0077] The up-sampled signal is supplied to an inter-picture predictor 8and a field decimator 11 for the same processing as the counterparts 8and 11 (FIG. 2).

[0078] The switch 10 selects fields from the input 60-fps interlacedmoving-picture video signal, different in time from frames selected bythe switch 3, as preprocessing in enhancement-layer coding.

[0079] The video signal having the fields as selected above is suppliedto a picture delayer 12, a subtracter 13, a DCT 14, a quantizer 15, anda variable-length encoder 16, for production of an enhancement-layerbitstream (a second bitstream), like the counterparts 12, 13, 14, 15 and16 in FIG. 2.

[0080] The enhancement-layer bitstream is supplied to a multiplexer 5for multiplexing this bitstream and the base-layer bitstream from theencoder 36. The multiplexed bitstream is little bit different from thatof the multiplexer 5 (FIG. 2), due to down-sampling and up-sampling.

[0081] The scanning up-sampler 38 and the field decimator 11 may becombined to directly produce the field video signal that is producedthrough the local decoder 37 to the decimator 11 in FIG. 4.Nevertheless, the processing through the local decoder 37 to thedecimator 11 in FIG. 4 is appropriate for, for example, half-pixelmotion compensation which requires pictures of double density in thevertical direction.

[0082] Disclosed next are embodiments of moving-picture temporalscalable decoding apparatus according to the present invention.

[0083] Shown in FIG. 5 is a first embodiment of a moving-picturetemporal scalable decoding apparatus according to the present invention,which is compatible with the moving-picture temporal scalable codingapparatus shown in FIG. 2.

[0084] In FIG. 5, a moving-picture bitstream supplied to a demultiplexer25 via a code input terminal 24 from, for example, the code outputterminal 6 shown in FIG. 2, is divided into a base-layer bitstream (afirst bitstream), an enhancement-layer bitstream (a second bitstream).

[0085] The base-layer bitstream is supplied to a decoder 21 to bereproduced into a 30-FPS progressive video signal. The decoder 21performs processing, an inverse version of the encoding processing bythe encoder 4 shown in FIG. 2.

[0086] The reproduced signal is supplied to a field decimator 22 and aninter-picture predictor 26. The field decimator 22 decimates theinterpolated scanning lines from the reproduced signal to obtain a fieldsignal. The field signal is supplied to a picture delayer 23 and storedtherein for several fields to be synchronized with fields of theenhancement-layer bitstream.

[0087] The enhancement-layer bitstream is supplied to a variable-lengthdecoder 30 so that variable-length codes of prediction residual isreconverted into fixed-length codes.

[0088] The fixed-length codes are supplied to a dequantizer 31 fordequantization at a given quantization parameter, thus reproduced intoDCT coefficients of prediction residual.

[0089] The DCT coefficients are supplied to an inverse DCT 32 so that8×8 DCT coefficients are converted into a decoded prediction-residualsignal.

[0090] The decoded prediction-residual signal is supplied to an adder33. Also supplied to the adder 33 is a prediction signal from theinter-picture predictor 26. The decoded prediction-residual signal andthe prediction signal are added to each other to be a 30-fps decodedvideo signal, such as, shown in FIG. 3C, having either even-number orodd-number fields of a 60-fps interlaced moving-picture video signal.

[0091] The output video signal from the picture delayer 23 and thedecoded video signal from the adder 33 are selectively output via aswitch 27 and an output terminal 28 in synchronism with the scale factorsupplied by the demultiplexer 25 in accordance with a parity of fields.The selectively output signal is a 60-fps interlaced moving-picturevideo signal.

[0092] Shown in FIG. 6 is a second embodiment of a moving-picturetemporal scalable decoding apparatus according to the present invention,which is compatible with the moving-picture temporal scalable codingapparatus shown in FIG. 4.

[0093] Elements shown in FIG. 6 the same as or analogous to those shownin FIG. 5 are given the same reference numerals and not explained indetail.

[0094] The differences between the second embodiment in FIG. 6 from thefirst embodiment in FIG. 5 are that the former has a scanning up-sampler42 and a decoder 41.

[0095] In FIG. 6, a moving-picture bitstream supplied to a demultiplexer25 via a code input terminal 24 from, for example, the code outputterminal 6 shown in FIG. 4, is divided into a base-layer bitstream (athird bitstream), an enhancement-layer bitstream (a second bitstream).

[0096] The base-layer bitstream is supplied to the decoder 41 toreproduce a 30-FPS progressive video signal. The decoder 41 operates inthe same way as the counterpart 21 shown in FIG. 5. The amount ofprocessing by the decoder 41 is, however, smaller than that by thecounterpart 21, due to fewer number of scanning lines caused bydown-sampling and up-sampling performed in coding, such as, shown inFIG. 4.

[0097] A reproduced video signal is supplied from the decoder 41 to thescanning line up-sampler 42 so that the number of scanning lines of thereproduced video signal is returned to the original number beforedown-sampling in coding (FIG. 4).

[0098] The up-sampled video signal is then supplied to a field decimator22 and an inter-picture predictor 26.

[0099] The scanning line up-sampler 42 is the same as the counterpart 38shown in FIG. 4 in operation. The field decimator 22, a picture delayer23, a switch 27, the inter-picture predictor 26, and another fielddecimator 29 are the same as the counterparts shown in FIG. 5 inoperation.

[0100] The enhancement-layer bitstream is subjected to decoding by avariable-length decoder 30, a dequantizer 31, an inverse DCT 32, anadder 33, the inter-picture predictor 26, and the field decimator 29,the same as the counterparts shown in FIG. 5 in operation.

[0101] The resultant signal is a 30-fps decoded video signal havingeither even-number or odd-number fields of a 60-fps interlacedmoving-picture video signal. It is then supplied from the adder 33 tothe switch 27 for selective video-signal output.

[0102] Discussed next with reference to FIGS. 7 and 8 is the structureof moving-picture temporal scalable bitstreams according to the presentinvention.

[0103] An exemplary moving-picture temporal scalable bitstream structureaccording to the present invention consists of base-layer bitstreams towhich a 30-FPS progressive video signal is coded and enhancement-layerbitstreams to which even-number or odd-number fields of a 60-fpsinterlaced moving-picture video signal are coded.

[0104] Such a bitstream structure is illustrated in FIG. 7 in which thesigns “Prog.” and “field” indicate one frame of a progressive videosignal and one field of an interlaced moving-picture video signal,respectively, with- numerals indicating the order of input pictures.

[0105] Base-layer pictures (1-frame progressive signal) come beforeenhancement-layer pictures (1-field interlaced video signal) forbi-directional prediction of the enhancement-layer pictures, even thoughthe former pictures come after the latter pictures in the time domain.The reverse order is further required among the base-layer pictures whenbi-directional prediction is performed for these pictures.

[0106] Illustrated in FIG. 7 is multiplexing per field in whichprogressive base-layer bitstreams each for one frame and interlacedenhancement-layer bitstreams each for one field appear alternately.These bitstreams may, however, not always appear alternately perpicture. In other words, these bitsteams may be put in different packetsand multiplexed on a timely basis.

[0107] Another exemplary moving-picture temporal scalable bitstreamstructure according to the present invention is illustrated in FIG. 8 inwhich base-layer bitstreams (“Frog.”) are transmitted beforeenhancement-layer bitstreams (“field”) for multiplexing.

[0108] In this invention, base-layer bitstreams of a coded 30-FPSprogressive video signal and enhancement-layer bitstreams of codedeven-number or odd-number fields of a 60-fps interlaced moving-picturevideo signal can be stored in a storage medium per packet with indexinformation indicating the base or the enhancement layer.

[0109] It is enough for such a storage medium that the base-layerbitstreams can only be reproduced. The reproduction of the base-layerbitstreams only according to the present invention offers higherresolution than the known temporal scalable coding technique. This isbecause the base-layer bitstreams carry progressing video signal in thisinvention whereas those carry either the even- or odd-number of fieldsof an interlaced moving-picture video signal in the known codingtechnique.

[0110] The present invention further offers computer programs forachieving the function of the first (second) embodiment of themoving-picture temporal scalable coding apparatus and/or the first(second) embodiment of the moving-picture temporal scalable decodingapparatus, disclosed above.

[0111] Disclosed first with respect to a flowchart shown in FIG. 9 is acomputer program for moving-picture temporal scalable coding.

[0112] Firstly, an interlaced moving-picture video signal supplied to acomputer is converted into a progressive moving-picture video signal atthe same frame rate (step S1). The processing in step S1 corresponds tothe operations of, for example, the progressive-scanning converter 2,the switch 3, and the picture selector 7 of the moving-picture temporalscalable coding apparatus shown in FIG. 2.

[0113] The progressive moving-picture video signal converted in step S1is coded to produce a base-layer bitstream (a first-bitstream) (step S2)while it is further locally decoded to produce a locally reproducedvideo signal. The processing in step S2 corresponds to the operationsof, for example, the encoder 4 and the local decoder 9 of themoving-picture temporal scalable coding apparatus shown in FIG. 2.

[0114] Fields of the input interlaced moving-picture video signal,different in time from frames of the progressive moving-picture videosignal are coded with inter-picture prediction using the locallyreproduced video signal as a reference video signal to produce anenhancement-layer bitstream (a second bitstream) (step S3). Theprocessing in step S2 corresponds to the operations of, for example, theinter-picture predictor 8, the switch 10, the field decimator 11, thepicture delayer 12, the subtracter 13, the DCT 14, the quantizer 15, andthe variable-length encoder 16 of the moving-picture temporal scalablecoding apparatus shown in FIG. 2.

[0115] The base-layer and enhancement-layer bitstreams are multiplexedwith each other as an output temporal scalable coded moving-picturevideo signal (step S4). The processing in step S4 corresponds to theoperation of, for example, the multiplexer 5 of the moving-picturetemporal scalable coding apparatus shown in FIG. 2.

[0116] In step S2, the progressive moving-picture video signal may bedown-sampled in the spatial vertical direction at the same frame rate asthe input interlaced moving-picture video signal before coded into thebase-layer bitstream (as a third bitstream), as disclosed for themoving-picture temporal scalable coding apparatus shown in FIG. 4.

[0117] Disclosed next with respect to a flowchart shown in FIG. 10 is acomputer program for moving-picture temporal scalable decoding.

[0118] Firstly, the temporal scalable coded moving-picture video signaloutput in step S4 of FIG. 9 is supplied to a computer and divided intothe base-layer bitstream (the first bitstream) and the enhancement-layerbitstream (the second bitstream) (step S11). The processing in step S11corresponds to the operation of, for example, the demultiplexer 25 ofthe moving-picture temporal scalable decoding apparatus shown in FIG. 5.

[0119] The base-layer bitstream is decoded into a progressivemoving-picture video signal (step S12). The processing in step S12corresponds to the operation of, for example, the decoder 21 of themoving-picture temporal scalable decoding apparatus shown in FIG. 5.

[0120] The reproduced progressive moving-picture video signal isconverted into a first field video signal having even-number (orodd-number) fields of an interlaced moving-picture video signal to bereproduced (step S13). The processing in step S13 corresponds to theoperations of, for. example, the field decimator 22 and the picturedelayer 23 of the moving-picture temporal scalable decoding apparatusshown in FIG. 5.

[0121] The enhancement-layer bitstream is subjected to inter-pictureprediction using the reproduced progressive moving-picture video signalas a reference picture signal, to be reproduced into a second fieldvideo signal having odd-number (or even-number) fields of the interlacedmoving-picture video signal to be reproduced, different in parity fromthe fields of the first field video signal (step S14). The processing instep S14 corresponds to the operations of, for example, thevariable-length decoder 30, the dequantizer 31, the inverse-DCT 32, theadder 33, the inter-picture predictor 26, and the field decimator 29 ofthe moving-picture temporal scalable decoding apparatus shown in FIG. 5.

[0122] The first field video signal and the second field video signalare switched and output as the reproduced interlaced moving-picturevideo signal (step S15). The processing in step S15 corresponds to theoperations of, for example, the switch 27 of the moving-picture temporalscalable-decoding apparatus shown in FIG. 5.

[0123] In step S12, the decoded progressive moving-picture video signalmay be up-sampled in the spatial vertical direction at the same framerate as the interlaced moving-picture video signal to be reproduced whenthe base-layer bitstream (the third bitstream) carries the down-sampledprogressive moving-picture video signal, as disclosed for themoving-picture temporal scalable decoding apparatus shown in FIG. 6.

[0124] In addition to the above embodiments, the present invention isapplicable, for example, to a transmitter for transmitting a temporalscalable coded moving-picture video signal and a receiver for receivingthe transmitted video signal.

[0125] Shown in FIG. 11 is a block diagram of an embodiment of atransmitter for transmitting a temporal scalable coded moving-picturevideo signal.

[0126] The computer program disclosed with reference to FIG. 9 istransmitted, over a network (not shown), to a receiver interface (I/F)71. The computer program is decoded and stored in a program buffer 72.

[0127] An interlaced moving-picture video signal is supplied to acomputer 73. The input video signal is subjected to the codingprocessing in accordance with the flowchart shown in FIG. 9 under thecomputer program supplied from the program buffer 72.

[0128] The resultant coded data is supplied to a transmitter interface(I/F) 74. The coded data is transmitted to the network in accordancewith a flowchart shown in FIG. 12.

[0129] In detail, the transmitter I/F 74 communicates with a recipientterminal over the network under a given protocol and determines whetherthere is transmission permission from the terminal (step S21).

[0130] If positive (YES in step S21), the transmitter I/F 74 convertsthe coded data into a given transmission format (step S22) and transmitsit to the network (step S23). On the contrary, if negative (NO in step521), the transmitter I/F 74 halts transmission of the coded data (stepS24).

[0131] In addition to the coded data, the transmitter I/F 74 maytransmit the computer program for decoding the coded data in accordancewith the flowchart shown in FIG. 10 so that a computer of the recipientterminal can decode the coded data under the computer program.

[0132] Shown in FIG. 13 is a block diagram of an embodiment of areceiver for receiving a temporal scalable coded moving-picture videosignal.

[0133] The following disclosure is made under the condition that codeddata of a temporal scalable coded moving-picture video signal and thecomputer program for decoding the coded data in accordance with theflowchart shown in FIG. 10 are transmitted over a network.

[0134] A receiver interface (I/F) 81 is connected to a network (notshown) and operates in accordance with a flowchart shown in FIG. 14.

[0135] In detail, the receiver I/F 81 determines whether a signaltransmitted over the network has been authenticated to be received (stepS31).

[0136] If positive (YES in step S31), the receiver I/F 81 receives anddecodes the coded data and the computer program (step S32). The receiverI/F 81 deformats the coded data and the computer program (step S33) andstores them in its memory (step S34).

[0137] On the contrary, if negative (NO in step S31), the receiver I/F81 halts receiving the coded data and the computer program (step S35).

[0138] The coded data stored in the memory of the receiver I/F 81 issupplied to a computer 82. The computer program also stored in thememory of the receiver I/F 81 is once stored in a program buffer 83 andthen supplied to the computer 82.

[0139] The computer 82 decodes the coded data under the computer programin accordance with the flowchart shown in FIG. 10, to reproduce aninterlaced moving-picture video signal.

[0140] The computer programs are supplied over the network in FIGS. 11and 13. Not only that, however, the computer programs may be reproducedfrom storage media.

[0141] As disclosed in detail, the present invention has severaladvantages. Some of these are as follows:

[0142] (1) Encoding an input interlaced moving-picture video signalafter converting it into a progressive moving-picture video signal atthe same frame rate as the interlaced moving-picture video signal, orencoding the progressive moving-picture video signal with the samenumber of scanning lines as the interlaced moving-picture video signal,drastically reduces the bit rate compared to encoding the inputinterlaced moving-picture video signal itself, in production of abase-layer bitstream (a first bitstream).

[0143] (2) Inter-picture prediction in producing an enhancement-layerbitstream (a second bitstream) using anterior and posterior referenceprogressive pictures both very close to a target picture to be predictedin the time domain, as illustrated in (c) of FIG. 3, achieves extremelyhigh coding efficiency with a small amount of codes generated, whichthus achieves temporal scalable coding to the input interlacedmoving-picture signal at high coding efficiency. This temporal scalablecoding is superior to the known temporal scalable coding technique andalso to the usual interlaced moving-picture coding on coding efficiency.

[0144] (3) The amount of coding processing with conversion of aninterlaced moving-picture video signal into a progressive moving-picturevideo signal at the same frame rate in this invention is larger than theknown temporal scalable coding technique. Nevertheless, it is less thanencoding interlaced moving-picture video signals after converting all ofthem into progressive signals.

[0145] (4) Production of a base-layer bitstream (a third bitstream) withencoding a progressive moving picture video signal having less scanninglines by down-sampling in the spatial vertical direction generates asmaller amount of codes than production of the same from a progressivemoving-picture video signal with no down-sampling. The input interlacedmoving-picture video signal, to be converted into the progressivemoving-picture video signal, has been suppressed for itsvertical-frequency components to be subjected to down-sampling to reducescanning lines, thus almost no decrease in resolution.

[0146] (5) Decoding and up-sampling the base-layer bitstream (the thirdbitstream) produced by encoding the progressive moving-picture videosignal down-sampled in the spatial vertical direction at the same framerate as an interlaced moving-picture signal to be reproduced, achievessmaller amount of decoding processing than decoding a bitstream of aprogressive moving-picture video signal with no down-sampling.

What is claimed is:
 1. A temporal scalable moving-picture video signalcoding method comprising the steps of: converting an input interlacedmoving-picture video signal into a progressive moving-picture videosignal at the same frame rate as the interlaced moving-picture videosignal; encoding the progressive moving-picture video signal to producea first bitstream; encoding fields of the interlaced moving-picturevideo signal, the fields being different in time from frames of theprogressive moving-picture video signal, with inter-picture predictionusing a locally decoded picture signal as a reference video signal, thelocally decoded picture signal being produced by locally decoding theprogressive moving-picture video signal, thus producing a secondbitstream; and multiplexing the first and second bitstreams into anoutput temporal scalable moving-picture video bitstream.
 2. A temporalscalable moving-picture video signal decoding method comprising thesteps of: demultiplexing a bitstream produced by temporal scalablemoving-picture coding into a first bitstream and a second bitstream, thefirst bitstream having been produced by encoding a progressivemoving-picture video signal at the same frame rate as an interlacedmoving-picture video signal to be reproduced, the second bitstreamhaving been produced by encoding fields of the interlaced moving-picturevideo signal, the fields being different in time from frames of theprogressive moving-picture video signal; decoding the first bitstream toreproduce a progressive moving-picture video signal; converting thereproduced progressive moving-picture video signal into a first fieldvideo signal having either even- or odd-number fields of the interlacedmoving-picture video signal; decoding the second bitstream withinter-picture prediction using the reproduced progressive moving-picturevideo signal as a reference video signal, thus producing a second fieldvideo signal having fields of the interlaced moving-picture videosignal, the fields of the second field video signal being different inparity from the fields of the first field video signal; and switchingthe first field video signal and the second field video signal to outputthe interlaced moving-picture video signal.
 3. A temporal scalablemoving-picture video signal coding apparatus comprising: a converter toconvert an input interlaced moving-picture video signal into aprogressive moving-picture video signal at the same frame rate as theinterlaced moving-picture video signal; a first bitstream generator toencode the progressive moving-picture video signal, thus generating afirst bitstream; a second bitstream generator to encode fields of theinterlaced moving-picture video signal, the fields being different intime from frames of the progressive moving-picture video signal, withinter-picture prediction using a locally decoded picture signal as areference video signal, the locally decoded picture signal beingproduced by locally decoding the progressive moving-picture videosignal, thus producing a second bitstream; and a multiplexer tomultiplex the first and second bitstreams into an output temporalscalable moving-picture video bitstream.
 4. The temporal scalablemoving-picture video signal coding apparatus according to claim 3further comprising a scanning-line down-sampler to which the progressivemoving-picture video signal obtained by the converter is supplied, thedown-sampler down-sampling the progressive moving-picture video signalin a spatial vertical direction to produce a progressive moving-picturevideo signal having a smaller number of scanning lines than theprogressive moving-picture video signal obtained by the converter,wherein the progressive moving-picture video signal having the smallernumber of scanning lines is supplied to the first bitstream generator,thus a third bitstream having the smaller number of scanning lines beinggenerated, and the second bitstream generator has a scanning-lineup-sampler to up-sample a locally decoded video signal in the spatialvertical direction, the locally decoded video signal being obtained bylocally decoding the third bitstream to produce a video signal havingthe same number of scanning lines as the progressive moving-picturevideo signal supplied to the down-sampler, the produced video signalbeing uses as the reference video signal.
 5. A temporal scalablemoving-picture video signal decoding apparatus: a demultiplexer todemultiplex a bitstream produced by temporal scalable moving-picturecoding into a first bitstream and a second bitstream, the firstbitstream having been produced by encoding a progressive moving-picturevideo signal at the same frame rate as an interlaced moving-picturevideo signal to be reproduced, the second bitstream having been producedby encoding fields of the interlaced moving-picture video signal, thefields being different in time from frames of the progressivemoving-picture video signal; a first decoder to decode the firstbitstream to reproduce a progressive moving-picture video signal; aconverter to convert the reproduced progressive moving-picture videosignal into a first field video signal having either even- or odd-numberfields of the interlaced moving-picture video signal; a second decoderto decode the second bitstream with inter-picture prediction using. thereproduced progressive moving-picture video signal as a reference videosignal, thus producing a second field video signal having fields of theinterlaced moving-picture video signal, the fields of the second fieldvideo signal being different in parity from the fields of the firstfield video signal; and a switch to switch the first field video signaland the second field video signal to output the interlacedmoving-picture video signal.
 6. The temporal scalable moving-picturevideo signal decoding apparatus according to claim 5, wherein thedemultiplexer demultiplex the bitstream produced by temporal scalablemoving-picture coding into the second bitstream and a third bitstreamproduced by encoding a progressive moving-picture video signaldown-sampled in a spatial vertical direction at the same frame rate asthe interlaced moving-picture video signal to be reproduced, the firstdecoder decoding the third bitstream into the down-sampled progressivemoving-picture video signal and up-sampling the down-sampled and decodedprogressive moving-picture video signal in the spatial verticaldirection, and the converter converting the up-sampled progressivemoving-picture video signal into the first field video signal.
 7. Acomputer-implemented method for temporal scalable moving-picture videosignal coding comprising the steps of: converting an input interlacedmoving-picture video signal into a progressive moving-picture videosignal at the same frame rate as the interlaced moving-picture videosignal; encoding the progressive moving-picture video signal to producea first bitstream; encoding fields of the interlaced moving-picturevideo signal, the fields being different in time from frames of theprogressive moving-picture video signal, with inter-picture predictionusing a locally decoded picture signal as a reference video signal, thelocally decoded picture signal being produced by locally decoding theprogressive moving-picture video signal, thus producing a secondbitstream; and multiplexing the first and second bitstreams into anoutput temporal scalable moving-picture video bitstream.
 8. Acomputer-implemented method for temporal scalable moving-picture videosignal decoding comprising the steps of: demultiplexing a bitstreamproduced by temporal scalable moving-picture coding into a firstbitstream and a second bitstream, the first bitstream having beenproduced by encoding a progressive moving-picture video signal at thesame frame rate as an interlaced moving-picture video signal to bereproduced, the second bitstream having been produced by encoding fieldsof the interlaced moving-picture video signal, the fields beingdifferent in time from frames of the progressive moving-picture videosignal; decoding the first bitstream to reproduce a progressivemoving-picture video signal; converting the reproduced progressivemoving-picture video signal into a first field video signal havingeither even- or odd-number fields of the interlaced moving-picture videosignal; decoding the second bitstream with inter-picture predictionusing the reproduced progressive moving-picture video signal as areference video signal, thus producing a second field video signalhaving fields different in parity from the fields of the first fieldvideo signal; and switching the first field video signal and the secondfield video signal to output the interlaced moving-picture video signal.